As a piezoelectric vibration element used in oscillation devices, bandpass filters, and the like, a crystal vibrator that uses vibration in a thickness shear mode as main vibration is widely used. As such a crystal vibrator, for example, a mesa-structure is known in which, in order to confine the vibration energy of vibration in a thickness shear mode, an etching process is performed to make a vibration portion thicker than a peripheral portion of the vibration portion. The mesa-structure includes excitation electrodes on both principal surfaces of the vibration portion, and extension electrodes electrically connected to the excitation electrodes. In this case, the extension electrodes extend through a step formed by the vibration portion and the peripheral portion.
Typically, the cross-sectional shape of the step formed by the vibration portion and the peripheral portion is determined depending on the orientation of the crystallographic axes of a crystal. An electrode may be broken on the side on which the angle formed by a lateral surface of the vibration portion and a surface of the peripheral portion is an acute angle. The extending direction of the electrodes may be limited, or it may be difficult to maintain stable quality in view of reliability of electrical connection.
On the other hand, for example, a configuration like the one in Patent Document 1 (identified below) is known in which an electrode electrically connected to the excitation electrode extends to the side on which the angle formed by the lateral surface of the vibration portion and the surface of the peripheral portion is an obtuse angle (toward first long-edge side in transverse direction). With this configuration, the electrode extends outward over the excitation electrode in the width direction, and the crystal vibrator may not be reduced in size.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2008-236439.